Cyclic AMP (cAMP) is an important second messenger which is involved in relaxation of respiratory tract smooth muscles and control of inflammatory cells, and the messenger is decomposed by phosphodiesterase (hereinafter abbreviated as “PDE” in the specification) to be converted into inactive 5′-AMP. Therefore, it is believed that suppression of the decomposition of cAMP by PDE may increase the concentration of cAMP, thereby bronchodilatation and anti-inflammatory action can be achieved. For this reason, PDE inhibitors having inhibitory action against the decomposition of cAMP have been focused as medicaments for the treatment of asthma, chronic obstructive pulmonary disease (hereinafter abbreviated as “COPD” in the specification) and/or other inflammatory diseases. In addition, five PDE isozymes (PDE I, II, III, IV and V) have recently been isolated, and their specific tissue distributions have been revealed (Adv. Second Messenger Phosphoprotein Res., 22, 1 (1988): Trends Pharm., Sci., 11, 150 (1990)).
Among inhibitors for these isozymes, in particular, inhibitors specific for PDE IV have been suggested to be possibly useful for the treatment of asthma, COPD and/or other inflammatory diseases (Thorax 46, 512 (1991) etc.). Herein, chronic articular rheumatism, atopic dermatitis, psoriasis, etc., are listed as concrete examples of the inflammatory disease. As a compound having specific inhibitory activity against PDE IV, for example, the compound disclosed in Japanese Patent Unexamined Publication (Kokai) No. 50-157360/1975 (Rolipram) has been known. 
Although various compounds have been known as PDE IV inhibitors (for example, compounds disclosed in Japanese Patent Unexamined Publication (Kokai) No. 4-253945/1992, International Patent Publication in Japanese (Kohyo) Nos. 6-504782/1994, 7-504442/1995, 8-501318/1996 and 9-500376/1997 and so forth), they have not been used clinically so far, and development of novel compounds having PDE IV inhibitory activity has been desired.